How to keep going for a long time

During a MMF or MFF, it's important to have stamina. Not only physical stamina (hit the gym), but also not cumming too fast.

If you're doing a MFF and the girls aren't experienced, the threesome critically relies on you having an erection. The moment you cum, it also dissolves into friendly chatter but no more sexual vibe (until you initiate again).

During MMF, there's another guy, which makes it awkward to cum too fast, as you'd ruin the MMF experienced, turning it into a normal one-on-one session with some watching.

Here's a couple of things that help a lot:

1. Use condom. Except that it's way safer, it will prolong sex (can be used by bf of couple).
2. Have sex or jerk off the night before you're going to do have group sex.
3. Take breaks. Use your fingers and tongue.
4. During DP and DPP, the bottom guy doesn't move much, which gives him some rest (take turns).